Sulphur based surface passivation for high voltage GaAs Schottky diodes

Surface passivation of high voltage GaAs Schottky diodes by sulphur containing solutions is investigated. A range of diodes with maximum voltage ratings in excess of 100 V were fabricated using Na2S or (NH4)(2)S-x chemical treatments prior to Schottky deposition. It is demonstrated that, whilst Na2S might provide an efficient passivation at low reverse biases, diodes passivated with this chemical showed little reduction in reverse leakage current under high reverse voltages. By contrast, (NH4)(2)S-x is shown to be an effective surface passivation under reverse bias in excess of 200 V - reducing leakage currents by at least two orders of magnitude in simple diodes (from 10(-2) to 10(-4) A cm(-2)) and extending the breakdown voltage of mesa terminated diodes from 150 to 250 V. (C) 1988 Elsevier Science Ltd. All rights reserved.